Strongly enhanced critical current density in MgB₂/Fe tapes by stearic acid and stearate doping

Abstract

Fe-sheathed MgB2 tapes with cheap stearic acid, Mg stearate and Zn stearate doping were prepared through the in situ powder-in-tube method. It is found that Jc, Hirr and Hc2 were significantly enhanced by doping. Compared to the pure tapes, Jc for all the doped samples was improved by more than an order of magnitude in a high-field regime. At 4.2 K, the transport Jc reached 2.02 × 104 A cm−2 at 10 T for the Zn stearate doped tapes and 3.72 × 103 A cm−2 at 14 T for the stearic acid doped samples, respectively. Moreover, at 20 K, Hirr for the Zn stearate doped tape achieved 10 T, which is comparable to that of the commercial NbTi at 4.2 K. The improvement of Jc–H properties in doped samples can be attributed to the increase of Hc2 resulting from the incorporation of C atoms into the MgB2 crystal lattice as well as a high density of flux-pinning centres.